Aerosol formulations of finely divided solid medicaments with anionic surface-active agents

ABSTRACT

AEROSOL FORMULATIONS ARE PROVIDED COMPRISING A FINELY DIVIDED SOLID MEDICAMENT, A PROPELLANT, AND AN ANIOMIC SURFACE-ACTIVE AGENT SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL, AMMONIUM AND AMINE SALTS OF DIALKYL SULPHOSUCCINC ACIDS WHEREIN THE ALKYL GROUPS CONTAIN FROM 4 TO 12 CARBON ATOMS, AND A ALKALI METAL, AMMONIUM AND AMINE SALTS OF ALKYLBENZENE SULPHONIC ACIDS WHEREIN THE ALKYL GROUPS CONTAIN FROM 8 TO 14 CARBON ACIDS.

United States Patent M AEROSOL FORMULATIONS OF FINELY DIVIDED SOLID MEDICAMENTS WITH ANIONIC SUR- FACE-ACTIVE AGENTS Philip Saxtou Hartley, Springfield, Kegworth, England,

assignor to Fisons Pharmaceuticals Limited, Loughborough, Leicestershire, England No Drawing. Continuation-impart of application Ser. No. 324,222, Nov. 18, 1963. This application July 5, 1968, Ser. No. 742,521

Int. Cl. A61c 27/00 US. Cl. 424-46 5 Claims ABSTRACT OF THE DISCLOSURE Aerosol formulations are provided comprising a finely divided solid medicament, a propellant, and an anionic surface-active agent selected from the group consisting of alkali metal, ammonium and amine salts of dialkyl sulphosuccinic acids wherein the alkyl groups contain from 4 to 12 carbon atoms, and alkali metal, ammonium and amine salts of alkylbenzene sulphonic acids wherein the alkyl groups contain from 8 to 14 carbon acids.

This application is a continuation-in-part application of application Ser. No. 324,222, filed Nov. 18, 1963, now abandoned.

The present invention relates to powdered medicament formulations for use in pressurized dispensing containers (hereinafter termed aerosol formulations and containers).

Aerosol formulations find wide use inter alia, as a means of applying a medicament to a patient, for ex ample by way of inhalation. In general, such formulations comprise the material to be dispensed in admixture with a propellant therefor, which propellant is usually a liquefied material which is gaseous at ambient t mperatures. Such formulations are held in a container provided with a valved outlet, which may or may not be adapted to release uniform doses of material, the volatilisation of the liquefied material generating a pressure within the container. Upon operation of the valved outlet, the contents of the container are discharged as a fine spray. The general construction of the container and valved outlet are well known in the aerosol art, as is the use of a wide variety of liquefied materials, notably halogenated hydrocarbons, as propellants.

Where the material to be dispensed is not soluble in the propellant material to be used, as may be the case with a finely divided solid medicament, it is necessary to have present in the aerosol formulation a suspending agent to ensure that the solid material is satisfactorily suspended. Hitherto it has been considered necessary to use surface-active agents which were non-ionic in nature to achieve satisfactory suspension of the solid medicament and other materials, since ionic surface-active agents were considered to have too low a solubility in the liquefied propellant medium to be effective. The non-ionic surfaceactive agents which are in current commercial use include the ethylene oxide condensates of phenols and esters or partial esters of fatty acids. Typical of such compounds are those materials sold under the trademarks Span and Arlacel. Furthermore, it has also been considered necessary to use comparatively large amounts of these materials to achieve satisfactory results and the use of 100% or more by weight of surface-active agent based on the weight of solid material to be suspended is commonplace in commercial formulations. I

It will be appreciated that in a pharmaceutical composition, especially one which is to be ingested, e.g. inhaled, by the user, it is highly desirable that the composition Patented Feb. 2, 1971 contain the minimum of materials, other than those which are clearly inactive diluents, which could in any way affect the user detrimentally. However reduction in the amounts of non-ionic surface-active agents in formulations of the type described above has resulted in formulations in which the solid materials were not satisfactorily suspended.

Surprisingly, I have found that certain anionic surfaceactive agents may be used as suspending agents in powder aerosol formulations, and that these anionic surface-active agents may be used at far lower concentration than has been hitherto considered necessary for the non-ionic surface-active agents in present use. The use of the anionic surface-active agents of the invention has the advantages that the amount of material in the formulation other than the pharmaceutical may be reduced to a level below that hitherto attained; that certain desirable propellants of low toxicity which are incompatible with non-ionic surface-active agents may be used; and that a material, which is water-soluble and hence does not inhibit the assimilation of the powdered medicament upon presentation to the mucous membranes, is used whereas non-ionic surface-active agents are generally water-insoluble and cover the powder particles as a comparatively thick waterinsoluble coating. A further surprising feature of the use of the anionic surface-active agents of the invention is that in many cases the amount of surface-active agent required to suspend the solid material does not depend directly on the amount of solid material present. Thus, it is possible to obtain adequate suspension of powdered medicament present as up to 5% by weight of the total formulation with 0.004% by weight of the total formulation of sodium dioctyl sulphosuccinate, i.e. using amounts of surface-active agent to medicament ranging from say 0.4% by weight at 1% medicament to 0.08% by weight at 5% medicament. This is to be contrasted with the nonionic surface-active agents which require to be used in much larger amounts and in amounts more directly proportional to the amount of solid present.

The fact that the anionic surface-active agents of the invention should be effective at all in powder aerosol formulations is wholly unexpected since other commonly used anionic surface-active agents have been found to be totally ineffective, in that they were not sufficiently soluble in the propellant medium to provide solutions of equivalent concentration to those used with non-ionic surface-active agents and at the very low concentration of compound in liquefied propellant medium, which could be achieved before the compounds themselves came out of solution, they were not effective as suspension acids.

Accordingly, the present invention provides a composition which comprises (a) a finely divided solid medicament having a particle size of less than microns, (-b) a propellant and (c) an anionic surface-active agent selected from the group consisting of (i) alkali metal, ammonium and amine salts of dialkyl sulphosuccic acids wherein the alkyl groups contain from 4 to 12 carbon atoms, and (ii) alkali metal, ammonium and amine salts of alkylbenzene sulphonic acids wherein the alkyl groups contain from 8 to 14 carbon acids; said medicament comprising from 0.025 to 20% by weight of the composition and said anionic surface-active agent comprising from about 0.01% to about 10% by weight of the solids content of the composition.

The surface-active agents for present use are preferably selected from the group comprising the salts of dialkyl sulphosuccinic acids wherein the alkyl groups are the same and contain from 4 to 9 carbon atoms, notably the salts of dibutyl-, dioctyland dinonylsulphosuccinic acids; and the salts of alkylbenzene sulphonic acids wherein the alkyl groups contain from 10 to 12 carbon atoms,

notably decyland dodecylbenzene sulphonic acids. The salts for present use may be the alkali metal, ammonium or amine salts of the acids. It will be appreciated that the salts should be selected from amongst those which are therapeutically acceptable. It is preferred to use the sodium salts of the acids.

The medicament is a finely divided solid, having a particle size of less than 100 microns, and preferably is of a particle size of 1-25 microns. Examples of medicaments which may be used include isoprenaline sulphate, atropine methonitrate, adrenaline acid tartrate, ephedrine hydrochloride, ergotamine tartrate, diphenhydramine hydrochloride, hydrocortisone acetate; antibiotics, for example penicillins, streptomycin and tetracycline; and mixtures of any of these together or with other medicaments. The medicament suitably comprises 0.025-20% by weight of the total composition, although larger or smaller proportions may be used if desired. According to a preferred embodiment the total composition contains 0.1-2% by weight of medicament.

The anionic surface-active agent may, as indicated above, be used in very small amounts. The amount of the surface-active agent required is broadly related to the solids content of the suspension and to the particle size of the solids. In general it is only necessary to use 0.0l-2% of the anionic surface-active agent by weight of the solids content of the suspension. It is not necessary to use larger amounts than this and I have found that the use of amounts in excess of from 5% to of the solids content of the suspension provides no advantage. Thus for example, with a suspension of a medicament for inhalation purposes where the composition contains 1% of solids of particle size about 10 microns, satisfactory suspension is obtained using 0.05 to 0.2% of the anionic surface-active agent by weight of the total solids in the composition. However, as indicated above, in some cases it may be possible adequately to suspend widely varying amounts of a powder with a given amount of anionic surface-active agent. The optimum amount of surface-active agent for any given formulation may be readily determined by simple tests of the type exemplified below.

The propellant may be any of the conventional propellants used in aerosol formulations, for example halogenated hydrocarbons of the fluorohydrocarbon or fluorohalohydrocarbon type such as trichloromonofiuoromethane, dichlrodifiuoromethane, dichlorotetrafluoroethane, monochlorotrifiuoromethane, monochlorodifluoromethane and mixtures of any of these together or with other propellants. Typical of suitable propellants are those disclosed in, for example, US. Pat. 2,868,691 and sold under the trademark Freon. As indicated above, it is possible to use certain non-toxic propellants which are incompatible with non-ionic surface-active agents. This is of special benefit when the formulation is to be ingested by the user, eg by inhalation, as opposed to being used externally, e.g. fOr the topical application of an antibiotic dust.

Where the formulations are to be ingested it is preferred to use as liquefied propellants either difluorodichloromethane or dichlorotetrafluoroethane, or mixtures thereof.

It will be appreciated that the various components of the composition of the invention should desirably be substantially anhydrous, that is that the minimum feasible amount of water should be present.

In some cases it may be desirable to add a polar solvent to the formulation; suitable polar solvents for this purpose include ethyl alcohol and isopropyl alcohol.

It may also be desired to add auxiliary solids to the formulation. Thus where the medicament is of density considerably less than that of the propellants, it may be suitable to add a solid inert diluent of high density of the same particle size, so that the density of the combined solids is similar to that of the propellants. Suitable inert solids for this purpose include sodium chloride and sodium sulphate.

The following examples are given to illustrate the present invention in which all percentages are by weight.

EXAMPLE 1 The following composition was prepared and incorporated in a pressurised aerosol package.

Percent Isoprenaline sulphate (particle size 28 microns) 0.1 Atropine methonitrate (particle size 2-8 microns) 0.04 Sodium dioctylsulphosuccinate 0.002 Dichlorotetrafiuoroethane 40 Dichlorodifluoromethane to This composition is useful for the relief of asthmatic conditions and used as in inhalant gives a dry spray which is readily absorbed by the mucous membranes. Furthermore, the solid material remained in suspension for a considerably longer period than when no surface-active agent was present.

EXAMPLE 2 Percent Isoprenaline sulphate (particle size 2-8 microns) 0.1 Atropine methonitrate (particle size 2-8 microns) 0.04 Sodium dibutylsulphosuccinate 0.002 Dichlorotetrafluoroethane 40.00

Dichlorodifluoromethane to 100%.

This composition is useful for the relief of asthmatic conditions and used as an inhalant gives a dry spray which is readily absorbed by the mucous membranes.

The composition was a stable suspension whose settling time was considerably longer than when no surfaceactive agent was present.

EXAMPLE 3 Percent Ephedrine hydrochloride (particle size below 20 microns) 1.0 Sodium chloride (particle size below 20 microns) 1.0 Naphazoline nitrate (particle size below 20 micons) 0.1 Cineole 0.2 Sodium dioctylsulphosuccinate 0.015 Dichlorodifluoromethane 30.0

Dichlorotetrafluoroethane to 100% This formulation is useful as a nasal decongestant. The composition was a stable suspension Whose settling time was considerably longer than when no surface-active agent was present.

Dichlorodifluoromethane to 100%.

EXAMPLE 5 A stable suspension was prepared from the following:

Percent Diphenhydramine hydrochloride (particle size below 25 microns) 0.5 Sodium dinonylsulphosuccinate 0.003 Ethyl alcohol 740.P 2.5 Dichlorodifluoromethane 30.0 Dichlorotetrafluoroethane to 100%.

EXAMPLE 6 A stable suspension was prepared from the following:

Percent Hydrocortisone acetate (particle size below microns) 0.4 Sodium dodecylbenzene sulphonate 0.004 Dichlorotetrafiuoroethane 40.0 Dichlorodifluoromethane to 100%.

6 ume of the aerosol spray and generally affects the ease of use of the composition.

(3) The times taken for the top quarter and the top half of the liquid phase to become substantially clear of suspended solid particles. This is a measure of the stability of the suspension and the tendency of the solid particles to flocculate.

The results of these examinations are set out in Table I below.

TABLE 1 Concentration (percent Settling w./w.) of Ease of time solid resus- Surface-active agent material Appearance pension 25% Sodium dioctylsulphosuccinate 0.05 Slightly flocculant Fair-- 1'19 2'40 0. 075 Very slightly flocculanL. Good 27" 4'9" 0.1 Smooth. 0. 25

1. 0 10.0 do Sorbitan trioleate 0. 05 Flocculant.

0. 1 0. 5 1. 0 do 5110.00 Fairly smoot Control (no surfactant) Flocculant Poor".-. 0'55 1'46 EXAMPLE 7 Examples 1 to 6 demonstrate the formation of stable suspensions using a variety of surface-active agents at concentrations of from 1.8% to 0.6% by weight of the solid medicament present. In all cases the stability of the suspension of the solid material was of the same order, which was considerably greater than when no surfaceactive agent was present.

In order to demonstrate the formation of stable suspensions over a wider range of concentrations, a series of suspensions were prepared using sodium dioctylsulphosuccinate as follows:

Ephedrine hydrochloride (of particle size less than 11 microns, 1%) was suspended in a solution of the surfaceactive agent (varying amounts) in monofluorotrichlord methane (to 100%) and the mixture subjected to high speed stirring in a Guisti stirrer for 5 minutes. By way of comparison, suspensionswere also prepared in the same manner using a typical non-ionic surface-active agent in current use in powder aerosol formulations, Arlacel 85 which is sorbitan trioleate. The suspensions were examined for:

(1) Appearance, since the smoothness of the suspension is an indication of the extent of dispersion of the solid medicament particles.

(2) The ease of re-suspending the suspension after it had been allowed to settle out. This has a profound effect upon the dosage of medicament supplied in a given vol- From the results shown in Table 1 it will be seen that the anionic surface-active agent was an effective suspension aid over a wide range of low concentrations; that it was more effective than the non-ionic material even when used at 5% of the concentration of the nonionic; and that it was not until the concentration of the non-ionic surfaceactive agent was raised to 50.0% that it showed an im provement in effe'ctivity when compared to a concentration of 0.075% of anionic material, i.e. the non-ionic material was present in some 800 times as great an amount.

Furthermore, the results of Table 1 show that the nonionic surface-active agent showed no significant improvement over the control suspension until it was present in a concentration of 10% or more.

I claim:

1. A substantially anhydrous composition consisting essentially of (a) a finely divided solid medicament having a particle size less than microns, (b) a halogenated hydrocarbon propellant having no more than 2 carbon atoms and (c) an anionic surface-active agent se lected from the group consisting of sodium dioctylsulphosuccinate and sodium dodecylbenzene sulphonate; said medicament being present in from 0.025 to 20% by weight of the composition and said anionic surface-active agent being present in from about 0.05% to about 2% by weight of the solids content of the composition.

2. The composition as claimed in claim 1 wherein the anionic surface-active agent is sodium dioctylsulphosuccin-ate.

7 8 3. The composition as claimed in claim 2 wherein the 3,131,152 4/1964 Klausner 167-39A sodium dioctylsulphosuccinate is present in a minimum 2,953,284 9/1960 Prussen et a1 42446 amount of about 0.075% by weight of the solids con ent 3,095,355 6/1963 Abramson 42446 of the composition; 3,169,095 2/1965 Thiel 42446 4. The composition as claimed in claim 1 whereln the 5 3,282,781 11/1966 Macek anionic surface-active agent is sodium dodecylbenzene sulphonate OTHER REFERENCES The composition as claimedfin claim 1 further 9 Di Giacomo: Drug and Cosmetic Industry, September taining an inert high denslty so11d of the same particle 1958; 79 3, me as the medlcament' 10 Schwartz et al.: Surface Active Agents and Detergents,

References Cited vol. II (1958), pp. 312-313.

UNITED STATES PATENTS STANLEY J. FRIEDMAN, Primary Examiner 2,889,243 6/1959 Underwood et a1. 167-82A 

